O(n²)

  @elements.each do |element|
    ...
    @elements.select{...}.each do |child|
      ...
    end
  end
            

Hash It!

O(n)

  @element_hash.each do |parent, children|
    ...
  end
            

70%↗

Slow Iteration?

  @elements.each do |element|
    render :partial => "..."
  end
            

Use Collection

  render :partial => "...", :collection => @elements
            

20%↗

Fact!

link_to is 3 times slower than raw url

40%↗

Performance Comparison

In total,

86%↗

Ajax Call

with loading spinner